The purpose of this research is to develop and evaluate the use of surgically implanted, thermally regulating ferromagnetic implants for inducing hyperthermia in tumors. The research can be grouped into two broad categories: 1. The clinical evaluation of the existing seeds in a number of clinical sites. This clinical work focusses on Phase I type trials where efficacy of heating is the primary endpoint and the development of clinical techniques, procedures and possibly instrumentation is the principal research process. We propose to take advantage of the clinical facilities of the University of Arizona, the University of California at San Francisco, and the City of Hope Medical Center. 2. The further development of the method by introducing better ferromagnetic materials and seed configurations and by introducing a permanently implanted version of the seeds. Both of these categories of research are bolstered by the development of better instrumentation and methods of characterizing the implants and by the development of quality assurance tests and procedures. It is anticipated that randomized clinical trials will be developed and introduced subsequently in later years of the grant, but the detailed specification of these are premature until experience is obtained in Phase I.